v8/test/mjsunit/regress/regress-10802.js
Arno Renevier d022b74c4e [builtins] Use fast path for JSArray source in TypedArray.from()
For TypedArray, a fast path is used when using the builtin iterator, and
next method has not been overriden. If we use that fast path for JSArray
too, the method will be about 200x times faster on a large array.

This patch also fixes a bug when a typed array is modified during the
mapper execution. In that case, the modification should not be taken
into account.

Bug: v8:10802

Change-Id: I74e2cbcd6a654def318585b4e08745037584669a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2358749
Commit-Queue: Arnaud Renevier <arenevier@fb.com>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69655}
2020-09-01 20:53:19 +00:00

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JavaScript

// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
const arr = new Uint8Array([1, 2, 3]);
function mapper(x) {
arr[1] = 182;
return x + 1;
}
assertArrayEquals([2, 3, 4], Uint16Array.from(arr, mapper));